From Sahih Bukhari (Hadith 2578):
Narrated `Aisha:I intended to buy Barirah but her masters stipulated that her Wala should be for them. When the Prophet was told about it, he said to me, "Buy and manumit her, as the Wala' is for the liberator." Once Barirah was given some meat, and the Prophet (ﷺ) asked, "What is this?" I said, "It has been given to Barirah in charity." He said, "It is sadaqa for her but a gift for us." Barirah was given the option (to stay with her husband or to part with him). `Abdur-Rahman (a sub-narrator) wondered, "Was her husband a slave or a free man?" Shu`ba (another sub-narrator) said, "I asked `Abdur-Rahman whether her husband was a slave or a free man. He replied that he did not know whether he was a slave or a free man
Reference: Bukhari 2578